Motor vehicles of the generic type with an energy coupling device for wireless magnetic coupling of an energy source external to the motor vehicle for wireless transmission of energy by means of an alternating magnetic field are known in basic principle, so that a separate documentation of publications to this end is not needed. The motor vehicle has the energy coupling device in order that energy can be supplied to the motor vehicle and preferably stored in the electric energy storage unit of the motor vehicle for the purpose of implementing its intended operation, such as, for example, its drive mode. The energy is supplied by means of the energy source external to the motor vehicle, such as, for example, a charging station or the like, which, on its part, is connected to an electric energy source, for example to a public energy supply grid, an electric generator, a battery, and/or the like. The charging station produces the alternating magnetic field with uptake of electric energy from the electric energy source. The energy coupling unit of the motor vehicle detects the alternating magnetic field by means of the coil, takes energy from it, and supplies electric energy at the motor vehicle end, in particular to supply the electric energy storage unit of the motor vehicle and/or also an electric engine of the drive device with electric energy.
The motor vehicle generally has an electrical system, which, in particular in the case of an electrically drivable motor vehicle, comprises an electrical drive unit for the motor vehicle. Beyond this, the electrical system generally also comprises the electric energy storage unit, which is usually designed as a rechargeable battery. In electrically drivable motor vehicles, the electric energy storage unit is often constituted by a high-voltage battery. The high-voltage battery can comprise, for example, a lithium ion rechargeable battery or the like. The electric energy storage unit supplies the electric energy for, among other things, the intended operation of the electrical system.
Motor vehicles of the generic type comprise the energy coupling device for supplying electric energy for the electrical system. Energy coupling devices that have a coil for wireless magnetic coupling of an energy source that is external to the motor vehicle and provides a magnetically alternating field are finding increasing use. In this way, an electromechanical coupling of the motor vehicle to the energy source external to the motor vehicle for supplying electric energy—for example, a connection of the motor vehicle to a charging station by means of a charging cable or the like—is no longer required. Nevertheless, said electromechanical coupling can also still be provided as an option. Advantages thereby ensue for the user of the motor vehicle in regard to service thereof, because, namely, a mechanical linkage—for example, by means of a charging cable or the like—is not needed for the purpose of energy coupling. In order that the energy coupling device can transform the energy supplied by means of the alternating magnetic field to electric energy and supply it to the electrical system, the coil is connected to a rectifier unit of the electrical system.
Because the vehicle body is generally constructed at least in part from an electrically conductive material, such as, for example, metal plate and, in particular, sheet metal, it is generally provided that the electrical system as well as the energy coupling device are arranged electrically insulated with respect to the vehicle body.
In systems in which energy is transmitted by means of an alternating magnetic field, also referred to as inductive energy transmission systems, the inductances of participating coil circuits are altered by variation of the distance of separation and/or by variation of a displacement.
During operation of a system for wireless energy coupling and, in particular, for inductive energy coupling, a large number of interferences, in particular electromagnetic interactions, can cause radio frequency interferences and/or the like, for example. At the energy source end, it is possible by means of classical measures of interference suppression, such as, for example, interference suppression filters and/or the like, to well attenuate these interferences, so that a required electromagnetic compatibility (EMC) can generally be achieved in this regard by appropriate damping or the like, so that the intended operation of all electrical devices can essentially be ensured in a reliable manner.
However, on account of the conversion principle, emitted interference occurs at the motor vehicle end, which, on the one hand, can be suppressed only poorly; and on the other hand, classical filtering measures are often accessible only to an inadequate extent. For example, a source of interference results in that, in correspondence to the alternating magnetic field, the coil of the energy coupling device provides an electric alternating current voltage at its terminals, which, for the purpose of supplying energy to the electrical system of the motor vehicle, is rectified by means of the rectifier unit. The rectifier unit usually comprises a bridge rectifier. Voltage jumps can occur that can lead to undesired emitted interference. However, such problems can also occur during operation at a half-wave rectifier, a full-wave rectifier, or like circuits.
In this case, among other things, a problem has proven to be that, on account of the rectifying function, the electric voltage at the terminals of the coil can be subject to high rates of change ensuing from the intended operation. As a result of this, both conductor-associated and non-conductor-associated emitted interference can be released, said emitted interference extending into frequency regions in which wireless-based communication takes place, such as, for example, medium-wave regions, short-wave regions, ultrashort-wave regions, television (TV) regions, digital audio broadcasting (DAB) regions, and/or the like.
The motor vehicle generally has the antenna unit, which serves for providing a wireless-based communication link. Through the arrangement of the antenna unit on the vehicle body, which is generally arranged as electrically insulated as well, electromagnetic and, in particular, capacitive coupling can result in an in-coupling of interferences produced by the coil during intended operation, so that interference voltages can be in-coupled into the antenna unit and interfere with, if not even totally prevent, the intended operation of the antenna unit for providing the wireless-based communication link.
WO 2010/060062 A1 further discloses a reduced interference between receivers and wireless power transmitters. Furthermore, DE 10 2013 225 241 A1 discloses a field shielding during inductive charging. In addition, WO 2016/030114 A1 discloses an inductive energy transmission system. Finally, EP 2 808 196 A1 discloses a transmitter element.